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 A138598 Numbers k such that |2^(2*k-27)-27| is prime. 0
 15, 16, 17, 23, 25, 305, 1277, 2675, 3179, 8987, 9013, 27493, 42703 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 2^(2*17-27)-27=101, 2^(2*23-27)-27=524261, 2^(2*25-27)-27=8388581, ... MATHEMATICA q=27; For[i=q, i<=q, a={}; Do[x=2^(2*n-i)-i; If[PrimeQ[x], AppendTo[a, n]], {n, 20^2}]; Print["2^(2*n-", i, ")-", i, " ", a]; i=i+2] Select[Range[1000], PrimeQ[Abs[2^(2#-27)-27]]&] (* Harvey P. Dale, Nov 12 2015 *) PROG (PARI) is(n)=ispseudoprime(abs(2^(2*n-27)-27)) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Sequence in context: A214424 A358043 A090461 * A281879 A354626 A114841 Adjacent sequences: A138595 A138596 A138597 * A138599 A138600 A138601 KEYWORD more,nonn AUTHOR Vladimir Joseph Stephan Orlovsky, May 13 2008 EXTENSIONS a(7)-a(11) from Iain Fox, Jan 13 2018 a(12) from Iain Fox, Jan 16 2018 a(13) from Iain Fox, Jan 18 2018 STATUS approved

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Last modified March 26 08:40 EDT 2023. Contains 361529 sequences. (Running on oeis4.)